Volatile welding flux



Patented Nov. 11, 1941 UNITED STATES PATENT. OFFICE' VOLATILE WELDINGFLUX Arthur R. Lytle, Niagara Falls, N. Y., and Thomas H. Vaughn,

Trenton, Mich, assignors to Union Carbide and Carbon ResearchLaboratories, Inc., a corporation of New York No Drawing.

1939, Serial No. 250,140. plication January 1'1, 1940,

13 Claims.

action being derived principally from boric oxide.

formed by the decomposition in the flame of these volatile borates.

We have discovered that certain distilled lower alkyl borates, such asthe methyl, ethyl and isopropyl borates, may be used alone with manifestadvantage as volatile welding fluxes by passing a welding gas intocontact with. a body of the liquid flux. The distilled higher alkylborates also may .serve but, because of their low vapor pressures atatmospheric temperature, it usually is necessary to heat them whilecontacting the welding gas therewith. Alkyl borates purified bydistillation to isolate the non-distillable substances, such as boricacid, oxide, etc., may be used effectively in the process. The presencetherein of small amounts of volatile combustible impurities does notinterfere with the use of these fluxes. Preferably, the welding gas isdried prior to contacting it with the liquid flux, in the interests offlux economy and of fluxing uniformity. In so far as we know, pure alkylborates never previously have been used as volatile welding fluxes.

It further has been discovered that a strong and uniform fluxing actionmay be imparted to a welding or brazing flame by passing part or all ofthe welding gas flowing thereto into contact with an at leastapproximately azeotropic mixture or solution of a lower alkyl borate,such as trimethyl borate, and an organic solvent for the borate capableof forming therewith such a-zeotropic compositions of substantiallyconstant composition. Among such solvents may be mentioned methanol andethanol; certain ketones, such. as acetone and methyl isobutyl ketone(hexane) certain chlorinated solvents, such as perchlorethylene;- andvarious other solvents, such as acetonitrile. Both the distilled alkylborates per se and the at least approximately azeotropio mixturesthereof with volatile organic solvents are relatively inexpensive. Theundi-. luted distilled alkyl borates offer advantages in handling and inuse; and each of the fluxes may be completely used up withoutencountering welding difli-culties resulting from flux compositionchanges or the accumulation of solid non-volatile matter, particularlywhen employing dry or approximately anhydrous welding gas.

Original application January 10,

Divided and this a! Serial No. 314,240

' geously may,

- be performed; and the encrustations are We further have found that the'lower alkyl borates or mixtures of the invention advantafor somepurposes, be mixed with other volatile fluxes,-for example, withvolatile organic silicates, such as alkyl silicates-4. g., methyl andethyl silicate. The silicates decompose in the welding flame, formingSi02, which enhances the fluxing action of the boric oxide and providesother advantages. y

In the preparation of those volatile fluxes of the invention containingorganic borates and organic silicates, it is preferred to employdistilled,

and substantially dry or anhydrous alkyl borates and alkyl silicates, inview of the tendency of the borates and silicates to hydrolyze in thepresence of moisture, and release boric acid and silicic acid.

So far as we are aware, volatile borate fluxes have heretofore beenused, only in the welding of nickel and Monel metal. We have found thatthe fluxes of the invention may be used with very beneficial results inthe welding or brazing of other metals, such as copper, brass, bronze,low carbon steel, and high chromium ferrous alloys, forexample,-rustless iron and stainless steel, in the welding of whichsolid or liquid fluxes are customarily used. Such customary fluxes leavedeposits. or encrustations on the metal which must be removed beforesubsequent operations, such as plating or tinning, can in many casesexceedingly ,diflicult to remove. In gaswelding or brazing metals ofthis class, the fluxes of the invention produce exceptionally sound,clean welds which require no preparation whatever prior toplating ortinning.

While the volatile borate fluxes of the invention are satisfactory for awide variety of purposes, we have found that an admixture of a volatileorganic silicate, e. g., methylsilicate, is advantageous in many cases.In the welding of steel, such a mixture increases the fluidity of theweld and facilitates the welding operation,

coupons were then submitted to a standard corrosion test in boilingnitric acid. The comparative corrosion-resistance of the welds is setforth in Table. 1 in order of decreasing corrosion-resistancez' Table 1I lux mixture Flux composition (by weight) 94% of distilled (CHa)=BO=and 6% of (CH;)4SiO 88% of distilled (CHmBO; and 12% of (CH;) $iO4.

. 91% of distilled (CHmBO; and 9% of (039 81 i 97% of distilled (0151030; and 3% 01 (CH|) SiO 80% of distilled (CHa)sBOs and 20% of (CH=)4SiOStandard paste flux (borosilicate glass).

All welds made with volatile flux showed marked superiority incorrosion-resistance over those made with flux F. Results of the testindicate that more than 3% of the silicate in the mixture is preferable,and that 20% undesir ably high.

In another series of tests, high strength steel coupons were welded(brazed) with bronze welding rods of two different compositions, aselected portion of the welding gas being bubbled through the indicatedmixtures of ethyl borate and methyl silicate, as follows:

Table 2 Test Flux Rod g ig ig E 855 Remarks Pounds per square inchPercent 1 A 1 50,000 35 Dense fumes 2 i A 2 58, 000 35 Slight fume a B 151, 000 35 Less fume 4 B 2 58,000 31 Very little fume very definitelyinhibits zinc fuming, which is such an objectional feature of brazingoperations when Welding rods containing zinc are used.

The term distilled is used in the specification and claims to designatean alkyl borate and/or alkyl silicate, or a mixture or solution thereof,that is substantially free from solid or non-volatilizable materials,such as boric oxide and/or silica, and boric acid and/or silicic acid.Such a borate or silicate generally is prepared by a distillation. I

The term a welding gas is used in the specification and claims todesignate either a fuel gas adapted for use in welding and/or brazingoperations-such as acetylene, hydrogen, ethylene, propane and the like,or mixtures thereof-or a combustion-supporting gas such as oxygen; or anappropriate mixture of a fuel gas and a combushon-supporting gas. theflux composition into the fuel gas prior to mixing the latter with thecombustion-supporting gas.

This application is a division of our pending It is preferred tointroduce application, Serial No. 250,140, for improvement in Volatilewelding fluxes, filed January 10, 1939.

We claim:

1. A volatile flux for use in welding or brazing metals, said fluxconsisting of an alkyl borate and an alkyl silicate.

2. A volatile flux for use in welding or brazing metals, said fluxconsisting of a distilled alkyl borate and an alkyl silicate.

3. A volatile flux for use in welding or brazing stainless steel, saidvolatile flux comprising a distilled substantially dry alkyl silicateeffectively increasing the corrosion-resistance of welds made instainless steel.

4. A volatile flux for use in welding or brazing metals, said fluxconsisting of a distilled dehydrated alkyl borate and an alkyl silicate,and at least one dehydrated alcohol selected from the group consistingof methyl alcohol, ethyl alcohol and isopropyl alcohol; the alkyl estersconstituting at least about 25% of the said mixture.

5. A welding gas for use in welding and brazing metals, said gascontaining a mixture of an alkyl borate and an alkyl silicate.

6. Process for welding and brazing metals, which comprises supplyingwelding gases consisting of a fuel gas and a combustion-supporting gasto a welding zone to produce a welding flame; and introducing into oneor both of said welding gases a volatile flux comprising an alkylsilicate.

7. Process for welding and brazing metals,

which comprises supplying welding gases consisting of a fuel gas and acombustion-supporting gas to a welding zone to produce a welding flame;and

introducing into at least one of said welding gases a volatile fluxcomprising an alkyl borate and an alkyl silicate.

8. A volatile flux for use in welding or brazing metals, said fluxconsisting of distilled ethyl borate and methyl silicate.

9. A volatile flux for use in welding or brazing metals, said fluxconsisting of distilled ethyl borate and methyl silicate, andat leastone dehydrated alcohol selected from the group consisting of methylalcohol and ethyl alcohol; the said esters constituting at least about25% of the said mixture.

10. Process for welding and brazing metals, which comprises supplyingwelding gases consisting of a fuel gas and a combustion-supporting gasto a welding zone to produce a welding flame;

and introducing into one or both of said welding gases a volatile fluxcomprising ethyl borate and methyl silicate.

11. In the process of welding or brazing metals containing zinc, themethod of minimizing zinc fuming, which comprises subjecting the moltenmetal to the action of a flux comprising an alkyl silicate.

12. In the process of welding or brazing metals containing zinc, themethod of minimizing zinc fuming, which comprises subjecting the moltenmetal-in the welding or brazing zone to the action of a volatile fluxcomprising an alkyl borate and an alkyl silicate.

13. A welding gas for use in welding and brazing metals, selected fromthe group consisting of a fuel gas and a. combustion-supporting gas,said gas containing an alkyl silicate functioning as a welding andbrazing flux.

ARTHUR R. LYTLE. THOMAS H. VAUGHN.

